JP5374810B2 - Screen printing version - Google Patents

Description

The present invention relates to a screen printing plate, a printing method , a multilayer wiring structure, and an image display device.

  Conventionally, in a semiconductor device in which a transistor or a diode is formed on a substrate or a semiconductor wafer, a multilayer wiring structure is used to increase the degree of integration. In such a multilayer wiring structure, an interlayer insulating film having a via hole for electrically connecting the wiring is used.

  In recent years, an organic insulating film having a relative dielectric constant smaller than that of a silicon oxide film has been widely used as a material for an interlayer insulating film. However, since the photolithographic technique is used when forming the through-hole in the organic insulating film, there are problems that the number of steps of the manufacturing method is large and the cost is disadvantageous.

  On the other hand, the screen printing method is a method in which ink is placed on a mesh (screen printing plate) in which an emulsion is formed in a non-ejection area where ink is not ejected, and ink is ejected by sliding a squeegee and printing is performed. There is an advantage that the number can be reduced and the use efficiency of the material is high. As described above, since the screen printing method can form a fine pattern by a simple method, it has recently been used in a wiring process such as a transistor. However, there is a problem that it is not suitable for forming minute through holes. This is because, firstly, since the screen printing method is a dynamic process, the ink that flows under the non-ejection area of the screen printing plate during printing is printed on the substrate. Second, the surface of the ink having fluidity immediately after printing is flattened by gravity, and at the same time, a slight amount of bleeding occurs (leveling). Therefore, in the case of forming a minute through hole, there is a high possibility that the ink that has flowed under the non-ejection area during printing and the ink leveled from four sides after printing will fill the through hole. For this reason, the conventional method is limited to printing that forms a 100 μm square through hole. Furthermore, since the screen printing method is affected by multiple parameters such as clearance (distance between the screen plate and the substrate), squeegee angle, pressure, and speed, it is difficult to stably form minute through holes. In large-area printing, the number of through-holes with a proven track record is about 300 μm square.

Such a screen printing method is often used for embedding a via hole. However, in Patent Document 1, a paste film made of a conductive paste having a pattern in which island-shaped punched portions are formed in a contour defining the outer shape. Is used for printing. Specifically, as the negative pattern of the paste film, a plurality of outer portions corresponding to the outer region of the outline of the paste film, island-like portions corresponding to the island-shaped cutout portions, and a width narrower than the diameter of the island-like portions There is used a screen printing plate having a reinforcing connecting portion provided so as to connect the island-like portions to each other, and in which an emulsion region for prohibiting the passage of the conductive paste is formed. Thereby, the occurrence of printing bleeding can be suppressed, but since the reinforcing connecting portion becomes a non-ejection region, screen printing cannot be performed on the entire surface except the island-shaped punched portion.
Japanese Patent No. 3582480

In view of the problem of the prior art described above has a minute through-hole to be able to stably form a screen printing plate, and is formed by a printing method and the printing method Ru using the screen printing plate interlayer An object is to provide a multilayer wiring structure having an insulating film and an image display device.

The invention according to claim 1 has a discharge area for discharging the printing liquid and a non-discharge area where the printing liquid is not discharged, and printing is performed by discharging the printing liquid from the discharge area by sliding a squeegee. one excluding the screen printing plate, the non-discharge area is a polygon whose vertices point in contact with the squeegee and the first when sliding the squeegee, the corners including a point of contact with the squeegee and the first The above corner is replaced with a curve , and the width of the non-ejection area in the length direction of the squeegee increases from the point of first contact with the squeegee until the maximum value of the width is reached. Thereby, the screen printing plate which can form a minute through-hole stably can be provided.

  According to a second aspect of the present invention, in the screen printing plate according to the first aspect, the non-ejection area is axisymmetric with respect to an axis in a direction in which the squeegee slides. Thereby, it is possible to form a thick film having minute through holes with little variation.

According to a third aspect of the present invention, in the screen printing plate according to the first or second aspect , the diameter of the non-ejection area is 50 μm or more and less than 300 μm. In the present specification and claims, the diameter of a region means the length of one side of the smallest square including the region. Thereby, a minute through-hole can be formed stably.

According to a fourth aspect of the present invention, in the printing method, the printing liquid is printed using the screen printing plate according to any one of the first to third aspects. Thereby, a thick film having a minute through hole can be provided.

The invention according to claim 5 is the printing method according to claim 4 , wherein the printing liquid is an insulating paste. Thereby, an insulating film having a minute through hole is obtained.

According to a sixth aspect of the present invention, in the multilayer wiring structure, the interlayer insulating film is formed by the printing method according to the fifth aspect. Thereby, a miniaturized multilayer wiring structure can be provided.

According to a seventh aspect of the present invention, in the image display device, the interlayer insulating film is formed by the printing method according to the fifth aspect. Thereby, a thin and lightweight image display apparatus can be provided.

According to the present invention, a multilayer wiring structure and a minute through-hole to stably form a screen printing plate which can be, the screen printing method Ru using the printing plate and the interlayer insulating film which is formed by the printing method An image display device can be provided.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

  The screen printing plate of the present invention is a polygon having a vertex at the point of first contact with the squeegee when printing is performed by ejecting ink by sliding the squeegee, and the width in the longitudinal direction of the squeegee is It has a through hole pattern that gradually increases from the point of first contact with the squeegee to the maximum width. Thereby, at the time of printing, the sneaking of the ink under the through-hole pattern can be suppressed, and a fine through-hole can be stably formed even in printing of a large area.

  FIG. 1 shows an example of the screen printing plate of the present invention. In the screen printing plate shown in FIG. 1, a regular hexagonal through-hole pattern 2 is formed on a mesh 1, and the through-hole pattern 2 becomes a non-ejection area of ink during printing. Further, when printing is performed in the printing direction (direction in which the squeegee 3 is slid) in the drawing, each through-hole pattern 2 is a regular hexagon with the point of first contact with the squeegee 3 as an apex. The width in the longitudinal direction of the squeegee gradually increases until it reaches the maximum width of the through-hole pattern 2 from the point of contact with. Thereby, the thick film which has a through-hole can be formed. The length direction of the squeegee is normally orthogonal to the printing direction.

  In the present invention, by forming the through-hole pattern 2 in such a shape and arrangement that the apex is the first point of contact with the squeegee 3 during printing, ink wrap-around under the through-hole pattern 2 is suppressed. The mechanism can be described as follows.

  FIG. 2A shows an example of the through-hole pattern 2 in which the end on the side that first comes into contact with the squeegee 3 in the printing direction is a side. When printing is performed in the printing direction in the drawing and ink is ejected to a place other than the through-hole pattern 2, the ink flows as shown in the drawing. When the squeegee 3 passes through the through-hole pattern 2, the ink before the through-hole pattern 2 is damped to the through-hole pattern 2, but a part of the ink is placed under the through-hole pattern 2 by the pressure of the squeegee 3. Wrap around. At this time, the sneak-in ink may be printed in a region to be a through hole of the member to be printed and fill the through hole. Furthermore, the ink remaining in the through-hole pattern 2 adversely affects subsequent printing, so that the repeated printing stability is impaired.

  On the other hand, as shown in FIG. 2B, if the through hole pattern 2 has an apex at the end of the side that first contacts the squeegee 3 in the printing direction, the ink in front of the through hole pattern 2 is the through hole. Since the ink can flow on both sides along the side of the pattern 2, it is possible to suppress the ink from flowing under the through-hole pattern 2. As a result, it is possible to suppress the printing of the ink in the region to be the through hole by the wrapping ink, and to stably form the fine through hole.

  As shown in FIG. 2C, when the through-hole pattern 2 has a shape such as a circle or an ellipse that does not have a vertex, the ink wraps around the bottom of the through-hole pattern 2 as shown in FIG. ), But more than in the case of FIG. This is considered to be because when the squeegee 3 passes through the through-hole pattern 2, ink tends to flow on both sides of the through-hole pattern 2 in FIG.

  The screen printing plate of the present invention is particularly effective when the diameter of the through-hole pattern 2 is less than 300 μm, that is, when the length of the minimum square side including the through-hole pattern 2 is less than 300 μm. is there. Further, the lower limit of the diameter of the through hole pattern 2 depends on the wire diameter of the mesh 1 used in the screen printing plate, and it is theoretically possible to reduce the diameter of the through hole pattern 2 as the wire diameter of the mesh 1 becomes smaller. It becomes possible. The finest mesh 1 available at present is a woven wire rod having a wire diameter of about 10 μm at a density of 840 per inch. As shown in FIG. 9, the mesh 1 has an opening (discharge region). The diameter is about 20 μm. Generally, when the through-hole pattern 2 is supported by the mesh 1, each through-hole pattern 2 needs to contain two or more mesh intersections. This is because when the through-hole pattern 2 contains one intersection point of the mesh, the contact area between the mesh 1 and the through-hole pattern 2 is small, and thus the through-hole pattern 2 may drop off during printing. For example, when the through hole pattern 2 having a diameter of 40 μm is formed on the mesh 1, as shown in FIG. 9, it is difficult for the through hole pattern 2 to contain two intersections of the mesh, the diameter is 50 μm. If there are, it is possible to contain approximately two or more mesh intersections. Therefore, when the diameter of the through-hole pattern 2 is 50 μm or more, minute through-holes can be stably formed even in large-area printing. Further, when the wire diameter of the mesh 1 is about 15 μm, the diameter of the through-hole pattern capable of stably forming minute through-holes even in a large area printing is 80 μm or more.

  In the present invention, each through-hole pattern 2 is preferably line-symmetric with respect to the axis in the printing direction, as shown in FIG. As a result, the ink in front of the through-hole pattern 2 can flow evenly on both sides along the side of the through-hole pattern 2 during printing, thereby further suppressing the ink from flowing under the through-hole pattern 2. can do.

  In the present invention, the through-hole pattern 2 preferably has a shape in which one or more corners except the corner including the vertex that first contacts the squeegee 3 are replaced with a curve, and includes the vertex that first contacts the squeegee 3. A shape in which all corners except the corners are replaced with curves is particularly preferable. The through-hole pattern 2 has a corner including a vertex that first comes into contact with the squeegee 3 and the other corners are replaced with a curve, so that the ink outside the through-hole pattern 2 easily flows smoothly along the curve. Therefore, it is possible to further suppress the ink from flowing under the through-hole pattern 2. Further, since the corners of the printed through holes are replaced with curves, the surface tension of the edges of the through holes is equalized, and the occurrence of bleeding due to the flow of ink can be suppressed. In addition, as a curve which substitutes a corner, the curve which comprises a circle | round | yen, an ellipse, a parabola etc. is mentioned, However, If it is convex outside, it will not specifically limit. FIG. 3 shows a specific example of such a through hole pattern 2. (A) is a square with three corners replaced with a curve, (b) and (c) are diamonds with two corners replaced with curves, and (d) is a diamond with three corners replaced with curves. .

  In addition, on the principle of the screen printing method, the ink ejected from the screen printing plate causes a slight amount of bleeding at the same time that the surface is flattened by gravity, so the through-hole pattern in the screen printing plate of the present invention, The shape of the formed through hole does not exactly match.

  In the present invention, the through-hole pattern 2 can be formed by a known method. For example, after the photosensitive emulsion is coated on the mesh 1, it can be formed by using a photolithography technique.

  The thick film having a through hole of the present invention is formed by printing using the screen printing plate of the present invention. Specifically, after the ink is applied on the screen printing plate in a state where the screen printing plate is arranged on the printing member, as shown in FIG. 1, the squeegee 3 is placed on the screen printing plate to which the ink has been applied. Slide in the printing direction. As a result, ink is ejected from the ejection area other than the through-hole pattern 2 (non-ejection area) on the mesh 1 onto the printing member. Further, by drying (curing) the printed member on which the ink has been discharged, a thick film having through holes can be obtained.

  In the present invention, the ink used for forming the thick film having through holes is not particularly limited, and a known material containing a resin component, a filler, and a solvent can be used. In particular, in order to form a through-hole having a diameter of 300 μm or less, it is preferable to use an ink that does not easily flow during printing or drying. Specifically, the viscosity under a printing temperature condition is 100 Pa · second or more. An ink having a solid content volume ratio of 25% or more in the ink can be used.

  In the present invention, an insulating film having a through hole is obtained by forming a thick film having a through hole using an insulating material.

The thickness of the thick film having the through hole is determined by the formula (mesh thickness × opening ratio + thickness of the through hole pattern) × solid content volume ratio of the ink. Therefore, a thick film having a predetermined film thickness can be formed by appropriately adjusting each parameter.

  In the multilayer wiring structure of the present invention, the thick film (interlayer insulating film) having the through hole of the present invention and a plurality of electrodes are laminated in a predetermined arrangement, and the upper and lower electrodes of the interlayer insulating film are electrically connected through the through hole. It can form by connecting to. As a result, the manufacturing process is greatly reduced, and a miniaturized multilayer wiring structure is obtained. In order to electrically connect the upper and lower electrodes of the interlayer insulating film, it is preferable to embed a conductive layer in the through hole. At this time, it is more preferable to form an upper electrode on the upper part of the interlayer insulating film using a screen printing method and to embed a conductive layer in the through hole. As a result, the same apparatus can be used and the manufacturing process can be simplified.

  FIG. 10 shows an example of the multilayer wiring structure of the present invention. On the substrate, an interlayer insulating film having a through hole is formed on the transistor on which the gate electrode, the gate insulating film, the source / drain electrode, and the semiconductor layer are formed. Further, a conductive layer is embedded in the through hole, and an upper electrode is formed on the interlayer insulating film. The upper electrode and the conductive layer can be formed using a commercially available conductive paste containing a conductive material, and examples of the conductive material include silver, copper, aluminum, and carbon.

  The image display device of the present invention includes a transistor element in which a transistor and a pixel electrode are electrically connected in a grid pattern through a through-hole of a thick film (interlayer insulating film) having a through-hole of the present invention. It can be formed by laminating an image display element on an active matrix substrate. Thereby, a thin and lightweight image display apparatus can be obtained by a simple manufacturing process. In addition, as an image display element, a liquid crystal display element, an electrophoretic display element, and an organic EL element can be used. Thereby, there is little burden on eyes and a flat panel type or a flexible image display apparatus is obtained.

  FIG. 11 shows an example of the image display device of the present invention. On the substrate, an interlayer insulating film having a through hole is formed on the transistor on which the gate electrode, the gate insulating film, the source / drain electrode, and the semiconductor layer are formed. Further, a conductive layer is embedded in the through hole, and a pixel electrode is formed on the interlayer insulating film. The electrophoretic display element formed on the support substrate on which the transparent electrode is formed is joined to the active matrix substrate having such a configuration.

( Reference Example 1)
As a screen printing plate, a square through-hole pattern 2 having a side of 200 μm is arranged in a matrix at a pitch of 400 μm on a mesh 1 (200 mm × 200 mm) having a wire diameter of 23 μm and an aperture ratio of about 50% (see FIG. 4). Using. The through-hole pattern 2 is line-symmetric with respect to the axis in the printing direction in the figure, and has a vertex that first contacts the squeegee. The through-hole pattern 2 was formed by exposing a mesh coated with a photosensitive emulsion through a photomask having a through-hole pattern, developing, and drying.

  On a polycarbonate film substrate (220 mm x 220 mm) with a thickness of 120 μm, using a screen printing plate and a thick film paste, printing in the printing direction in the figure and then drying at 100 ° C. for 60 minutes yields a thick film It was. In addition, as thick film paste, what melt | dissolved polyvinyl alcohol resin in the solvent and added the filler and the viscosity modifier and adjusted the viscosity to about 200 Pa.second was used.

As a result of evaluating the obtained thick film using a length measuring microscope, a substantially square through hole was formed on the entire surface. In addition, the average side of the formed through-hole was 160 μm.
(Comparative Example 1)
A thick film was formed in the same manner as in Reference Example 1 except that the screen printing plate shown in FIG. 5A was used instead of the screen printing plate shown in FIG. The through-hole pattern 2 is line-symmetric with respect to the axis in the printing direction in the figure, and has a side that first contacts the squeegee.

As a result of evaluating the obtained thick film using a length measuring microscope, the irregular through-hole shown in FIG. 5B was formed on the entire surface. The formed through-holes were slightly shrunk in the printing direction, and the size was an average length of 160 μm × width of 145 μm.
(Example 2)
A thick film was formed in the same manner as in Reference Example 1 except that the through hole pattern 2 of the screen printing plate shown in FIG. 4 was changed to a through hole pattern having a diameter of 200 μm shown in FIG. Note that the through-hole pattern is line-symmetric with respect to the axis in the printing direction in the figure, and has a vertex that first contacts the squeegee.

In the obtained thick film, through holes having substantially the same shape as the through hole pattern were formed on the entire surface. The size of the formed through-holes was average length 160 × width 160 μm.
(Comparative Example 2)
A thick film was formed in the same manner as in Reference Example 1 except that the through hole pattern 2 of the screen printing plate shown in FIG. 4 was changed to a circular through hole pattern with a diameter of 200 μm shown in FIG.

  The obtained thick film had through-holes formed on the entire surface, and the formed through-holes were slightly shrunk in the printing direction, and the average size was 160 × 150 μm.

In contrast to Example 2, although the area of the through-hole pattern on the screen printing plate is smaller in Example 2, it can be seen that the formed through-holes are larger in Example 2.
(Example 3 and Comparative Example 3)
The screen printing plate has a through-hole pattern with a diameter of 350, 300, 250, 200, 150, 100 and 50 μm on a mesh having a wire diameter of 18 μm and an aperture ratio of about 40%, as shown in FIG. What formed the pattern part was used. In addition, as shown in FIG.7 (b), 1000 pieces of two types of through-hole patterns of a circular shape (comparative example 3) and a water drop shape (Example 3) were respectively arrange | positioned in each pattern part with a 500 micrometer pitch. At this time, the through-hole pattern was formed by exposing the mesh coated with the photosensitive emulsion through a photomask having the through-hole pattern, developing, and drying. Further, the through hole pattern of the water droplet shape (Example 3) is line symmetric with respect to the axis of the printing direction in the figure, has a vertex that first contacts with the squeegee, and extends in the printing direction and the length direction of the squeegee. The width is the same.

  On the washed glass substrate, using a screen printing plate and an insulating paste, printing was performed in the printing direction in the figure, followed by drying at 110 ° C. for 30 minutes to obtain an insulating film. The insulating paste used was prepared by dissolving polyvinyl butyral resin in a solvent, adding an inorganic filler having an average particle size of 0.1 μm, and adjusting the viscosity to about 400 Pa · sec.

  The obtained insulating film was observed with a microscope, and the number of through holes formed without being buried in each pattern portion was evaluated. Table 1 shows the evaluation results.

表１より明らかなように、貫通孔を安定に形成することができるのは、比較例３では、貫通孔パターンの径が３００μｍ以上の場合であるが、実施例３では、１５０μｍ以上である。
（実施例４）
ポリカーボネート基板上に、インクジェット法を用いて、ナノ銀インクを形成し、乾燥させることによって、ゲート電極を形成した。次に、スピンコート法を用いて、熱重合型ポリイミドを塗布し、１９０℃で熱処理することによって、ゲート絶縁膜を形成した。形成されたゲート絶縁膜は、比誘電率が３．６、膜厚が０．４μｍであった。ソース／ドレイン電極を形成する領域に、フォトマスクを介して、紫外線を照射することにより、表面改質を実施した。さらに、インクジェット法を用いて、ナノ銀インクを形成し、乾燥させることによって、ソース／ドレイン電極を形成した。次に、インクジェット法を用いて、構造式

As is clear from Table 1, the through-holes can be formed stably when the diameter of the through-hole pattern is 300 μm or more in Comparative Example 3, but 150 μm or more in Example 3.
Example 4
A nano silver ink was formed on a polycarbonate substrate using an inkjet method, and dried to form a gate electrode. Next, using a spin coating method, a heat-polymerizable polyimide was applied and heat-treated at 190 ° C., thereby forming a gate insulating film. The formed gate insulating film had a relative dielectric constant of 3.6 and a film thickness of 0.4 μm. Surface modification was performed by irradiating the region where the source / drain electrodes were formed with ultraviolet rays through a photomask. Further, nano-silver ink was formed using an ink jet method and dried to form a source / drain electrode. Next, using the inkjet method, the structural formula

で表される有機半導体材料をキシレンに溶解させることによりインク化したものを膜形成することによって、有機半導体層を形成し、有機トランジスタを得た。得られた有機トランジスタは、チャネル長が５μｍ、チャネル幅が２ｍｍであった。

An organic semiconductor layer was formed by dissolving an organic semiconductor material represented by the formula (2) in xylene to form an ink, whereby an organic transistor was obtained. The obtained organic transistor had a channel length of 5 μm and a channel width of 2 mm.

  As a screen printing plate, a through-hole pattern 2 similar to FIG. 6A is arranged in a matrix at a pitch of 300 μm on a mesh 1 (200 mm × 200 mm) having a wire diameter of 23 μm and an aperture ratio of about 50% (FIG. 8). Reference) was used. The through-hole pattern 2 is line-symmetric with respect to the axis in the printing direction in the figure, and has a vertex that first contacts the squeegee.

  An interlayer insulating film having a through hole was formed on the organic transistor by printing in the printing direction in the drawing using the screen printing plate and the insulating paste shown in FIG. 8 and drying. The insulating paste used was prepared by dissolving polyvinyl acetal resin in a solvent, adding an inorganic filler having an average particle size of 0.1 μm, and adjusting the viscosity to about 400 Pa · sec.

  Furthermore, by using a screen printing method, a silver paste made of Ag particles, an acrylic resin and a solvent is formed on the interlayer insulating film and dried to embed the conductive layer in the through hole of the interlayer insulating film and A pixel electrode conducting with the organic transistor was formed, and an active matrix substrate having transistor elements provided in a lattice shape was obtained.

  Next, 20 parts by weight of titanium oxide, 1 part by weight of acid polymer, 2 parts by weight of silicone polymer graft carbon black MX3-GRX-001 (manufactured by Nippon Shokubai Co., Ltd.) and 77 parts by weight of silicone oil KF96L-1cs (manufactured by Shin-Etsu Chemical Co., Ltd.) After mixing, the mixture was dispersed with an ultrasonic wave for 1 hour to prepare a black and white particle dispersion. Further, the black and white particle dispersion was microencapsulated using a gelatin-gum arabic complex coacervation method. At this time, the average particle size of the microcapsules was about 60 μm. An electrophoretic display element is obtained by spreading a dispersion obtained by dispersing the obtained microcapsules in a urethane resin solution on a film substrate with a transparent electrode film using a wire blade method to form a uniform microcapsule sheet. Got.

  The obtained electrophoretic display element was bonded to an active matrix substrate to obtain the image display device shown in FIG.

It is a figure which shows an example of the screen printing plate of this invention. It is a figure explaining the mechanism which suppresses the wraparound of the ink under a through-hole pattern. It is a figure which shows the specific example of a through-hole pattern. It is a figure which shows the screen printing plate of the reference example 1. FIG. It is a figure which shows the screen printing plate of the comparative example 1, and the formed through-hole. It is a figure which shows the through-hole pattern of Example 2 and Comparative Example 2. FIG. 6 is a diagram showing a screen printing plate of Example 3. FIG. 6 is a diagram showing a screen printing plate of Example 4. FIG. It is a figure explaining the minimum of the diameter of a through-hole pattern. It is a figure which shows an example of the multilayer wiring structure of this invention. It is a figure which shows an example of the image display apparatus of this invention.

Explanation of symbols

1 mesh 2 through hole pattern 3 squeegee

Claims (7)

In a screen printing plate that has a discharge area for discharging a printing liquid and a non-discharge area that does not discharge a printing liquid, and that prints by discharging the printing liquid from the discharge area by sliding a squeegee,
The non-ejection area is a polygon whose apex is a point first contacting the squeegee when the squeegee is slid, and one or more corners excluding a corner including the point first contacting the squeegee are curved. Is replaced with
The screen printing plate according to claim 1, wherein a width of the non-ejection area in the length direction of the squeegee increases from a point of first contact with the squeegee to a maximum value of the width.   The screen printing plate according to claim 1, wherein the non-ejection area is line-symmetric with respect to an axis in a direction in which the squeegee slides. 3. The screen printing plate according to claim 1, wherein a diameter of the non-ejection region is 50 μm or more and less than 300 μm. A printing method comprising printing a printing liquid using the screen printing plate according to any one of claims 1 to 3 . The printing method according to claim 4 , wherein the printing liquid is an insulating paste. A multilayer wiring structure comprising an interlayer insulating film formed by the printing method according to claim 5 . An image display device comprising an interlayer insulating film formed by the printing method according to claim 5 .

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